1. Field of the Invention
The present invention relates to ionographic systems for creating images and, in particular, to the method and apparatus to control the vertical line width in images created with such ionographic systems.
2. Description of the Prior Art
The problem of crosstalk between adjacent electrodes in an ionographic print head is known. For example, U.S. Pat. No. 4,558,334 discloses a two electrode ion generator producing ions only during the print period requiring reduced power to achieve given ion outputs, and includes low impedance gated oscillators to reduce capacitive crosstalk between the electrodes.
In some ionographic systems, the problem of crosstalk manifests itself in the difficulty of producing vertical lines in printed images. In such systems there is generally an array of adjacent modulating electrodes, each of the electrodes being driven by a gate receiving a strobe voltage and a data voltage to reproduce a black or white spot corresponding to a digital image signal. For example, the crosstalk phenomenon is evidenced in vertical lines on the reproduced images, lines parallel to the processing direction, that tend to start light and get darker and wider as they continue in the vertical direction until reaching a stable thickness and density. Also, the stable thickness is often too thin to the point that 1 bit wide vertical lines (lines of 1 bit or pixel length) are virtually nonexistent, and the widths of 2 bit wide vertical lines are approximately equal to the width of a 1 bit wide horizontal line. U.S. Pat. No. 4,794,412 to Casey et al. teaches of just such a phenomenon and indicates a way to reduce the crosstalk effects. Adjustment of the strobe and data voltages applied to the ionographic array gates which drive the ion modulators reduced the amount of crosstalk between modulators. Specifically, by lowering the data voltage below the strobe voltage level, the crosstalk between modulators was reduced.
Unfortunately, system latitudes prevent the reduction of the data and strobe voltages to a point which would assure the ability to eliminate crosstalk field effects and the associated problem of printing fine vertical structures. Therefore, an additional method was needed to compensate for the crosstalk effects which would enhance the printed output and make the system less prone to the introduction of crosstalk errors.
It is an object of the present invention, therefore, to provide a new and improved method and apparatus to compensate for crosstalk in an ionographic printing device and in particular, to provide uniform and consistent output of vertical structure within images created by an ionographic printing device. It is another object of the present invention to enable the selective variation of the printed width for all vertical structure in printed output created with the ionographic device.
Further advantages of the present invention will become apparent as the following description proceeds, and the features characterizing the invention will be pointed out with particularity in the claims annexed to and forming a part of this specification.